Sunshine, temperature and suicidal behaviour in patients treated with antidepressants: an explorative nested case-control study.

Our aim was to explore if different exposure windows for sunshine or temperature are associated with increased suicidal behaviour among people starting antidepressant treatment. 307 completed and 1674 attempted suicides were included as cases in the conditional logistic regression analyses, while controlling for potential confounders, including season, as well as temperature and hours of sunshine when these variables were not the main exposure variable. Ten controls were matched to each case using risk-set sampling. The role of season, age, and sex was examined with likelihood ratio tests (LRTs) with and without the respective interaction terms and with stratified analyses. There was no overall association between temperature or sunshine with suicidal behaviour. Age was a significant effect modifier for suicide and suicide attempt for both sunshine and temperature exposure. In stratified analyses, an increase of one degree Celsius in the average daily temperature during the last 4 weeks was associated, in the unadjusted model, with a 3% increase in the rate of suicide (p = 0.023) amongst older patients (65+). In the same age group, an increase of 1 h in the average daily sunshine during the last 4 weeks was associated with an 8% increase in the rate of suicide attempt (p = 0.002), while the respective increase for the exposure period of 5-8 weeks was 7% (p = 0.007). An increase of one degree Celsius in the average daily temperature during the last 4 weeks was associated with a 3% increase in the rate of suicide attempt (p = 0.007). These associations did not retain statistical significance in the adjusted models. No associations were found in the other age groups. Our results point to a possible effect modification by age, with higher risk of suicidal behavior associated with an increase in sunshine and temperature found in the older age groups.

Season of treatment initiation with antidepressants and suicidal behavior: A population-based cohort study in Sweden.

BACKGROUND: Decreased binding capacity of SERT in the prefrontal cortex has been observed in both suicide victims and suicide attempters. Moreover, some studies have shown that SERT has a seasonal variation with lower binding capacity in the spring and summer, which coincides with a seasonal peak of suicides. Our aim was to explore whether the season of treatment initiation with antidepressants is associated with suicide or suicide attempt and compare it with the underlying suicide seasonality in the general population. METHODS: Using Swedish registers, patients who initiated treatment with an antidepressant were followed up to three months for suicidal behavior. Cox regression analyses were used. Results were compared with the underlying seasonal pattern by calculating standardized mortality ratios (SMRs) for suicides and standardized incidence ratios (SIRs) for suicide attempts. RESULTS: Patients aged ≥65 years had higher risk for suicide when initiating antidepressant treatment in the summer, and also a higher risk for suicide attempt when initiating treatment in the spring and summer. Young patients (0-24 years) presented a higher risk for suicide attempt when initiating treatment in the autumn. Patients with previous suicide attempt had a seasonal pattern, with a higher risk to carry out a suicide attempt in the summer and autumn. Results from the SMR and SIR calculations numerically support these findings. LIMITATIONS: We used information of filling an antidepressant prescription as a proxy of actual antidepressant treatment. Patients with combination, augmentation therapy or those switching antidepressant during follow-up were excluded. Thus, our results refer to less complicated psychopathology. CONCLUSIONS: Our results indicate an interaction between biological and health care-related factors for the observed seasonal pattern of suicidal behavior in the elderly, whereas psychological and societal factors may be more important for the seasonality observed in the younger patients.

Serotonergic medication enhances the association between suicide and sunshine.

BACKGROUND: An association between suicide and sunshine has been reported. The effect of sunshine on hormones and neurotransmitters such as serotonin has been hypothesized to exert a possible triggering effect on susceptible individuals. The aim of this study is to examine if there is an association between sunshine and suicide, adjusting for season, and if such an association differs between individuals on different antidepressants. METHODS: By using Swedish Registers and the Swedish Meteorological and Hydrological Institute we obtained information, including forensic data on antidepressive medication for 12,448 suicides and data on monthly sunshine duration. The association between monthly suicide and sunshine hours was examined with Poisson regression analyses while stratifying for sex and age and controlling for time trend and season. These analyses were repeated in different groups of antidepressant treatment. RESULTS: We found a significantly increased suicide risk with increasing sunshine in both men and women. This finding disappeared when we adjusted for season. Among both men and women treated with selective serotonin reuptake inhibitors (SSRIs) there was a positive association between sunshine and suicide even after adjustment for season and time trend for suicide. Pair comparisons showed that the sunshine-suicide association was stronger among men treated with SSRIs compared to other antidepressant medications or no medication at all. LIMITATIONS: Other meteorological factors were not controlled (i.e. temperature) for in the analyses. CONCLUSIONS: There is an enhanced association between sunshine and suicide among those with SSRI medication, even after adjusting for season. This may have interesting theoretical and clinical implications.